platform/x86: wmi: move struct wmi_device_id to mod_devicetable.h

In preparation for adding WMI support to MODULE_DEVICE_TABLE() move the
definition of struct wmi_device_id to mod_devicetable.h and inline
guid_string in the struct.

Changing guid_string to an inline char array changes the loop conditions
when looping over an array of struct wmi_device_id. Therefore update
wmi_dev_match()'s loop to check for an empty guid_string instead of a
NULL pointer.

Signed-off-by: Mattias Jacobsson <2pi@mok.nu>
[dvhart: Move UUID_STRING_LEN define to this patch]
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
diff --git a/include/linux/wmi.h b/include/linux/wmi.h
index 4757cb5..592f81a 100644
--- a/include/linux/wmi.h
+++ b/include/linux/wmi.h
@@ -18,6 +18,7 @@
 
 #include <linux/device.h>
 #include <linux/acpi.h>
+#include <linux/mod_devicetable.h>
 #include <uapi/linux/wmi.h>
 
 struct wmi_device {
@@ -39,10 +40,6 @@
 
 extern int set_required_buffer_size(struct wmi_device *wdev, u64 length);
 
-struct wmi_device_id {
-	const char *guid_string;
-};
-
 struct wmi_driver {
 	struct device_driver driver;
 	const struct wmi_device_id *id_table;